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J Weld Join > Volume 31(6); 2013 > Article
Journal of KWJS 2013;31(6):37-43.
DOI: https://doi.org/10.5781/KWJS.2013.31.6.37    Published online January 21, 2014.
A Study on Analyzing Thermal Strain of Weldment during Cooling used at Low MS Point Weld Consumables
Yunsok Ha, Seongkil Nam, Sejin Park, Changgil Kwon
Correspondence:  Yunsok Ha,
Email: yunsok.ha@samsung.com
This study targets to make clear the connection between MS (Martensite start) point and welding shrinkage. We approved that a Martensite-transformed weldment may not yield state under low MS point, but also admitted the limitation of numerical calculation by inherent strain approach or thermal strain approach. Therefore, new thermal strain formulae during cooling stages were made. As a thermal strain is obtained by integrating thermal extension coefficient, a constant of integration should be decided. In our suggested formulae, the origin was based on totally remained austenite, and added strain from volume changes in Martensite transformation was based on totally transformed ferrite. Through the suggested methodology, It is verified that an MS point under a critical temperature can let weld shrinkage relax and the critical value can be obtained. For supporting this process, 15 weld-consumables were made, were tested by fillet type and were measured. As a result, a positive correlation between MS point and level of weld-distortion was obtained, but it was rather weak.
Key Words: Martensite, Weld consumable, Transformation, Welding distortion, Fillet

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